Apparatus for blind stitch sewing

ABSTRACT

Sewing machine fittings are disclosed which serve particularly advantageously in producing a blindstitch hem in this invention, including a pair of needles arranged side-by-side one formed with a thread carrying eye and the other with a latch, and a throat plate fitted with a thread manipulating device for assisting in the concatenation of thread from the thread carrying needle to the latch needle on each stitch.

United States Patent 1191 Ketterer 1 Sept. 30, 1975 [54] APPARATUS FOR BLIND STITCH SEWING 3.194.197 7/1965 Ketterer et a1 112/202 X 3.3 .2 1 9 2 [75] Inventor: Stanley J. Ketterer, Jamesburg, NJ. 01 06 H 67 Ldnzendorfu H [73] Assignee: The Singer Company, New York, Primary Eraminer-Geo V. Larkin N.Y. Allorney, Age/1!, or FirmM. J. Breen; C. A. Filed: Nov. 1974 Williams, Jr.; R. E. Smith [21] Appl. No.: 527,315 [57] ABSTRACT Sewing machine fittings are disclosed which serve par- [52] US. CL. 112/197 i ularly advantageously in producing a blindstitch [51] lm. Cl. D05B 1/06; D05B 1/10 hem n hi n i n, in luding a p ir of needles ar- [58] Field of Search 112/197-2112, ranged r' one formed with a thread carrying 112/157, 158 R. 160, 184, 98, 168 eye and the other with a latch, and a throat plate fitted with a thread manipulating device for assisting in the [56] Referen e Cited concatenation of thread from the thread carrying nee- (C to the latch needle on each stitch.

2,636,461 4/1953 Mikolas 112/197 X 9 Claims, 13 Drawing Figures US. Patent Sept. 30,1975 Sheet 10f2 3,908,569

US. Patent Sept. 30,1975 Sheet 2 of2 3,908,569

APPARATUS FOR BLIND STITCH SEWING BACKGROUND OF THE INVENTION This invention relates to the art of blindstitch hemming; that is, the formation of stitches securing a hem fold in place in such fashion that the noticeability of the stitches on the face of the fabric is minimized.

Specialized commercial sewing machines have long been known for sewing true blind stitches. Since these machines can be used for no other purpose, they are not practical or economically feasible for household use.

The blindstitching arrangements which have heretofore been available for use with household sewing ma chines have required such tedious and skillful work manipulation as to render such arrangements impractical for use by most household sewing machine users. These prior arrangements such, for instance, as that disclosed in the U.S. Pat. No. 2,627,239 do not provide for stitching completely hidden from the fabric face but instead seek to minimize the appearance of the stitches on the fabric face. In the U.S. Pat. No. 2,627,239, the appearance of the stitches on the fabric face is minimized by use of a complicated Z-shaped fold of the hem together with use of a special zigzag stitch pattern which shifts the needle only periodically into a position for penetration of the face ply of the fabric and at other times locates the needle to one side where it does not form hem securing stitches but places a line of connecting stitches in the unexposed portion of the hem fold.

It is very difficult to direct the Z-shaped fold of goods to the sewing machine needle in such a way that during the infrequent lateral excursions of the needle, the needle merely grazes the edge of the upper fold edge. This is particularly true since for most of the stitches in the pattern, the needle occupies a different lateral position. To simultaneously give concern to preserving the total width of the hem fold while carefully guiding the edge of the top fold requires a level of skill which most household sewing machine users do not possess.

SUMMARY OF THE INVENTION It is an object of this invention to provide an arrangement for blindstitch hemming which may be performed on a household sewing machine and in which the work fabric need be presented to the stitching point with only a plain hem fold formed therein. This object of the invention is attained by the provision, in a sewing machine having a loop taker which traverses laterally across the line of stitch formations during loop seizing motion, of a pair of needles arranged sideby-side laterally of the line of stitch formation. One needle carries a sewing thread for the formation of chain stitches and the other needle is formed with a thread engaging hook for cooperation with the first needle in manipulating the thread carried by the loop taker from one needle to the other.

Another object of this invention is to provide means for insuring unerring manipulation of the thread by the sewing machine loop taker and needles in the formation of the blindstitch seam of this invention. This object of the invention is attained by the provision of a thread loop deflector carried by the sewing machine throat plate and actuated in timed relation to the stitch forming instrumentalities of the sewing machine for engaging and wrapping the thread from the thread carrying needle around the hook needle.

With the above and additional objects and advantages in view, as will hereinafter appear, this invention will now be described in detail with reference to a preferred embodiment illustrated in the accompanying drawings in which: 7

FIG. 1 represents a perspective view of a fragment of a sewing machine having this invention applied thereto and including work fabrics in which a blind stitch hem is being formed in accordance'with this invention;

FIG. 2 is a perspective view of the thread concatenation as viewed from the top during the formation of a seam in accordance with this invention;

FIG. 3 is a perspective view of the thread concatenation, including a fragment of the work fabrics, as viewed from the bottom during the formation of a seam in accordance with this invention;

FIG. 4 is a top plan view of a sewing machine throat plate including fragments of the sewing machine loop taker and work feed dog taken near the completion of a forward feed-stroke substantially at the beginning of needle penetration of the work;

FIG. 5 is a top plan view similar to that of FIG. 4 but taken near the completion of the idle return stroke of the feed dog as the needle is withdrawn from the work;

FIG. 6 is a perspective view of the underside of the throat plate;

FIG. 7 is an elevational view of the hook needle of this invention looking into the lengthwise groove;

FIG. 8 is an elevational view of the hook needle of this invention taken at right angles to that of FIG. 7;

FIG. 9 is an elevational view of the sliding latch for the hook needle as manufactured;

FIG. 10 is an elevational view of the hook needle showing the sliding latch being inserted therein;

FIG. 11 is an elevational view similar to FIG. 10 but showing the sliding latch positioned completely within the needle groove;

FIG. 12 is an elevational view of the completed needle of this invention, and

FIG. 13 is an elevational view of an assembly of both a threading carrying and a hook needle for use in this invention.

Referring to the drawings, 11 indicates a household sewing machine having a work supporting bed 12 and a bracket arm 13 overhanging the bed. A needle bar 14 endwise reciprocable in the bracket arm is associated with a skip stitching device indicated generally at 15 by which the endwise reciprocation of the needle bar may be suspended. The skip stitch mechanism which is illustrated, is built in accordance with the U.S. Pat. No. 3,559,601 of E. Tullman which is incorporated herein by reference although it will be understood that other mechanisms for suspending needle bar reciprocation may serve equally as well.

As shown in FIG. 1, the needle bar carries a pair of needles 20 and 30 arranged in side-by-side relation laterally of the line of work feed of the sewing machine as determined by a work feed dog 40 of a conventional four motion work feed mechanism, which feed dog works upwardly through slots 41 formed in a throat plate 42 carried on the sewing machine bed. The needles pass endwise through an elongated needle hole 43 in the throat plate.

Beneath the throat plate in the bed is disposed a loop taker 50 preferably rotatable on a vertical axis 51 ary ranged forwardly of the path of needle reciprocation. The loop taker may be constructed in accordance with that forming the subject of the US. Pat. No. 3,693,565 which is incorporated herein by reference and which is conventionally adapted to form lock stitches. As used in the present invention, however, a chain stitch seam will be formed and any conflict between lock stitch and chain stitch modes may be eliminated by removing all thread from the bobbin in the loop taker.

Of the pair of needles 20 and 30 carried on the needle bar 14, the needle 20 is a conventional threadcarrying sewing machine needle. The needle 30, however, is a hook needle. As will be described hereinbelow, the hook needle 30 disclosed in the drawings is a particularly advantageous form of construction, but a wide variety of hook needles could be utilized as well in carrying out the teachings of this invention.

As shown in FIG. 5, the thread T from the thread carrying needle 20 is seized during each needle penetration by the beak 52 of the loop taker 50 and carried laterally by the loop taker across the hook needle 30.

The hook needle on its next withdrawal from the work carries a loop L of the thread T upwardly through the work and through any previously seized loop of thread which may have been held on the hook needle.

7 As a result, the single thread chain stitch concatenation of FIG. 2 is formed by operation of the sewing machine depicted in FIG. 1.

In order to form a blind stitch hem in a garment 60, a plain hem fold 61 is formed inwardly from the face 62 of the garment along the garment edge and the hem folded garment is placed face down on the sewing machine bed in which position the hem fold is directed to the stitching point.

FIG. 3 illustrates the appearance of the single thread chain stitch seam from the face of the garment. The only thread segments which are visible are those which extend between the needles 20 and 30 during stitch formation. It is pointed out that the spacing between the needles 20 and 30 in FIGS. 1 to 3 is somewhat exaggerated for clarity of illustration, and that the closer the needles can be maintained, the less conspicuous will be the thread segments visible on the face of the garment. Particularly if a long stitch length is utilized, i.e. considerable distance is placed between successive needle penetrations along the length of the seam, and if suitable color of thread is chosen to blend with the color of the fabric, the segments of thread in the seam which do appear on the face of the garment can be made hardly noticeable. By use of the skip stitch mechanisms of the sewing machine, a stitch spacing is obtainable far in excess of the maximum which can be produced by use of the sewing machine feed mechanism alone.

The blind stitch seam illustrated in FIGS. 1, 2, and 3 can be produced using just the needles 20 and 30 and the loop taker 50. Greater certainty, however, of seizure of the thread T by the hook needle 30 can be attained by the provision of a thread deflecting means on the throat plate 42 as shown in FIGS. 4, 5, and 6 and which will now be described.

The underside 70 of the throat plate 42 is formed with a recess 71 having opposite straight sides 72 and 73 which define guiding surfaces for a reciprocating block 74 which is formed with slots 75 and 76 as well as an opening 77 adapted to embrace the feed dog 40 of the sewing machine so that the reciprocating block will partakeof the feed motions of the feed dog. The reciprocating block 74 is formed along one side with a notch 78 which is engaged by a tooth 79 projecting from an oscillating thread deflecting member 80 pivotally supported in the recess 71 beneath the throat plate on a headed rivet 81. The headed rivet 81 also projects over the reciprocating block 74 and cooperates with another headed rivet 82 which projects over the opposite side of the block to restrain the block in place between the recess sides 72 and 73.

The oscillating thread deflecting member 80 is formed with a curved arm 83 terminating in an offset thread engaging finger 84 adapted, as shown in FIG. 5, to engage and wrap the thread T around the hook needle 30 during the upstroke of the needles as the feed dog moves forwardly into position to begin a work feed stroke. The certainty of thread loop seizure by the hook needle is then greatly augmented by this provision of the thread loop deflecting means.

Although any one of a wide variety of hook needles may be utilized with this invention, the hook needle which forms a part of the preferred form of this invention, as disclosed in the accompanying drawings, is particularly advantageous because of its simplicity, ease of manufacture, and superior operating characteristics.

As shown in FIGS. 7 and 8, the hook needle 30 comprises a butt portion 90, shank 91 and pointed freeextremity 92 having interrelation similar to that of any conventional sewing machine needle. One lengthwise groove 93 is formed opening along one side of the needle and extending continuously from the butt to the pointed free extremity. Near the pointed free extremity the needle shank at one side of the groove 43 is formed with an inclined lateral slot 94 which opens onto the groove 93 to define a thread engaging hook 95. The needle shank at the side of the groove 93 opposite the thread engaging hook 95 is formed with a recess 96 serving to expose the thread engaging hook 95. At the butt 90, the sidewalls of the groove 93 are deformed at two spaced locations 97 and 98 to provide travel stops limiting sliding movement along the groove 93 of a latch member 100.

As shown in FIG. 9, the latch member 100 is preferably formed as a sheet metal stamping and includes a lengthwise elongate body portion 101 formed at one extremity with a small lateral extending stop lug 102 and at the other extremity with a laterally extending hook shield 103. Between the ends, the body portion 101 is formed with a lateral extension 104 of considerable length which, as shown in FIG. 12, will ultimately be wrapped around the needle shank to retain the latch member in the needle groove 93.

FIGS. 10, 11 and 12 illustrate the manner in which the latch member is assembled into the groove 93 of the hook needle 30. First, the stop lug is inserted into the groove beneath the bottom travel stop 97 with the latch member body arranged at right angles to the needle. The latch member is then turned 90 to position the body portion 101 in the groove with the stop lug arranged between the travel stops. Lastly, the extension 104 is deformed and wrapped loosely around the needle shank 91 to complete the hook needle. It will be noted that the hook shield 103 protrudes slightly out of the groove 93 so that it can be influenced by the passage of the needle into and out of work fabrics to effect relative movement of the latch member along the needle groove to the extent permitted by the travel stops 97 and 98..When the shield 103 occupies a position opposite the hook 95, moreover, the protrusion of the shield out of the groove 93 protects the hook preventing escape of thread loops thereon or inadvertent snagging of other fibers, for instance, fibers of the work fabric. In this position, the shield also serves as a guide to direct off the needle and past the hook any loops of thread which may be engaged thereon.

Having set forth the nature of this invention, what is claimed herein is:

l. A set of fittings for producing a blind stitch hem on a sewing machine having an endwise reciprocatory needle bar, a four motion work feed dog for establishing a line of stitch formation relatively to the path of reciprocation of said needle bar, and a loop taker including a beak movable in a loop seizing motion transversely across the line of stitch formation, said set of fittings comprising a needle assembly adapted to be secured to said needle bar and including a pair of needle blades arranged in parallel relation, that one of said needle blades toward which the loop taker beak approaches during loop seizing motion being formed with a thread accommodating eye pointed extremity, and the other of said needle blades being formed with an extremity provided with a thread engaging hook, and a throat plate having articulated thereunder a thread deflecting element operatively connected to said work feed dog to engage the thread seized by said loop taker beak from said thread carrying needle to deflect said engaged thread around said hook needle.

2. In a set of fittings as recited in claim 1 in which the hook needle of said needle assembly comprises an elongated body formed with an enlarged butt at one extremity, a shank, and a point at the opposite extremity, said hook needle body formed with a single continuous lenghtwise groove extending from said pointed extremity through said elongated butt, an inclined groove formed in said needle shank at one side of and intersecting said lengthwise groove to define said thread engaging hook on said needle at the juncture of said grooves, and a latch member slidably arranged in said lengthwise groove, said latch member including a lateral shield projection extending out of said lengthwise groove and movable into and out of a position adjacent to said thread engaging hook, said latch member including a lateral extension formed in spaced relation to said shield projection, said lateral extension being deformed into a ring loosely encircling said needle shank after assembly of said latch member into said lengthwise groove.

3. In a set of fittings as recited in claim 2 in which the hook needle of said needle assembly includes a shallow recess formed in the shank at the opposite side of said lengthwise groove from said thread engaging hook to expose said hook for ready engagement with a thread, and said shield projection of said latch member is movable into and out of a position in the lengthwise groove between said shallow recess and said thread engaging hook.

4. In a set of fittings as recited in claim 2 in which the hook needle of said needle assembly includes cooperating stop means formed on said needle body and on said latch member for limiting the sliding movement of said latch member along said lengthwise groove.

5. In a set of fittings as recited in claim 4 in which said stop means comprises a lateral stop projection formed on said latch member and spaced abutment means formed on said needle cooperating with said stop projection, each of said abutment means including a localized deformation of said lengthwise needle groove side wall.

6. In a set of fittings as recited in claim 1 in which the needle assembly comprises a-pair of needle blades each formed with a butt, means for securing said butts together with said needle blades in parallel relation, each of said needle blades being formed with a pointed free extremity, the pointed free extremity of one .of said needle blades being formed with a transverse thread accommodating eye, the other of said needle blades being formed with a thread engaging hook facing in a direction opposite the pointed free extremity thereof and arranged at a distance from the butt not less than that of the thread accommodating eye of said other needle blade.

7. In a set of fittings as recited in claim 6 in which said needle blade formed with a hook includes a single continuous lengthwise groove accommodating therein a sliding latch member shiftable into and out of a position adjacent to said thread engaging hook, and in which said lengthwise groove faces diametrically opposite from said other needle blade in said assembly.

8. In a set of fittings as recited in claim 7 in which said eye pointed thread carrying needle includes a lengthwise groove extending from said eye to said butt along one side of said needle blade, and in which the hook of the other needle blade of said assembly is formed on that side of said needle which faces in the same direction as the lengthwise groove of said eye pointed needle.

9. In a set of fittings as recited in claim 1 in which said throat plate carries on the underside a slide plate embracing said sewing machine feed dog means beneath said throat plate constraining said slide plate to reciprocate in the line of stitch formation with said feed dog, and in which said thread deflecting element comprises a lever pivoted beneath said throat plate and having an operative connection with said slide plate. 

1. A set of fittings for producing a blind stitch hem on a sewing machine having an endwise reciprocatory needle bar, a four motion work feed dog for establishing a line of stitch formation relatively to the path of reciprocation of said needle bar, and a loop taker including a beak movable in a loop seizing motion transversely across the line of stitch formation, said set of fittings comprising a needle assembly adapted to be secured to said needle bar and including a pair of needle blades arranged in parallel relation, that one of said needle blades toward which the loop taker beak approaches during loop seizing motion being formed with a thread accommodating eye pointed extremity, and the other of said needle blades being formed with an extremity provided with a thread engaging hook, and a throat plate having articulated thereunder a thread deflecting element operatively connected to said work feed dog to engage the thread seized by said loop taker beak from saiD thread carrying needle to deflect said engaged thread around said hook needle.
 2. In a set of fittings as recited in claim 1 in which the hook needle of said needle assembly comprises an elongated body formed with an enlarged butt at one extremity, a shank, and a point at the opposite extremity, said hook needle body formed with a single continuous lenghtwise groove extending from said pointed extremity through said elongated butt, an inclined groove formed in said needle shank at one side of and intersecting said lengthwise groove to define said thread engaging hook on said needle at the juncture of said grooves, and a latch member slidably arranged in said lengthwise groove, said latch member including a lateral shield projection extending out of said lengthwise groove and movable into and out of a position adjacent to said thread engaging hook, said latch member including a lateral extension formed in spaced relation to said shield projection, said lateral extension being deformed into a ring loosely encircling said needle shank after assembly of said latch member into said lengthwise groove.
 3. In a set of fittings as recited in claim 2 in which the hook needle of said needle assembly includes a shallow recess formed in the shank at the opposite side of said lengthwise groove from said thread engaging hook to expose said hook for ready engagement with a thread, and said shield projection of said latch member is movable into and out of a position in the lengthwise groove between said shallow recess and said thread engaging hook.
 4. In a set of fittings as recited in claim 2 in which the hook needle of said needle assembly includes cooperating stop means formed on said needle body and on said latch member for limiting the sliding movement of said latch member along said lengthwise groove.
 5. In a set of fittings as recited in claim 4 in which said stop means comprises a lateral stop projection formed on said latch member and spaced abutment means formed on said needle cooperating with said stop projection, each of said abutment means including a localized deformation of said lengthwise needle groove side wall.
 6. In a set of fittings as recited in claim 1 in which the needle assembly comprises a pair of needle blades each formed with a butt, means for securing said butts together with said needle blades in parallel relation, each of said needle blades being formed with a pointed free extremity, the pointed free extremity of one of said needle blades being formed with a transverse thread accommodating eye, the other of said needle blades being formed with a thread engaging hook facing in a direction opposite the pointed free extremity thereof and arranged at a distance from the butt not less than that of the thread accommodating eye of said other needle blade.
 7. In a set of fittings as recited in claim 6 in which said needle blade formed with a hook includes a single continuous lengthwise groove accommodating therein a sliding latch member shiftable into and out of a position adjacent to said thread engaging hook, and in which said lengthwise groove faces diametrically opposite from said other needle blade in said assembly.
 8. In a set of fittings as recited in claim 7 in which said eye pointed thread carrying needle includes a lengthwise groove extending from said eye to said butt along one side of said needle blade, and in which the hook of the other needle blade of said assembly is formed on that side of said needle which faces in the same direction as the lengthwise groove of said eye pointed needle.
 9. In a set of fittings as recited in claim 1 in which said throat plate carries on the underside a slide plate embracing said sewing machine feed dog means beneath said throat plate constraining said slide plate to reciprocate in the line of stitch formation with said feed dog, and in which said thread deflecting element comprises a lever pivoted beneath said throat plate and having an operative connection with said slide plate. 